Copying process utilizing a recording material comprising electrically conductive particles homogeneously dispersed in a deformable insulating polymeric substance

ABSTRACT

COPYING PROCESS WHICH COMPRISES IMAGEWISE EXPOSING TO ACTIVATING RADIATION A RECORDING MATERIAL COMPRISING ELECTRICALLY CONDUCTIVE PARTICLES HOMOGENEOUSLY DISPERSED IN A DEFORMABLE INSULATING POLYMERIC SUBSTANCE, SAID SUBSTANCE ALSO CONTAINING AT LEAST ONE SUBSTANCE CAPABLE OF GIVING OFF A GAS UNDER IRRADIATION, THERMALLY EXPANDING THE GAS THUS RELEASED, TO PRODUCE A LATENT IMAGE CONSISTING OF AREAS OF DIFFERENT CONDUCTIVITY ON SAID RECORDING MATERIAL, ELECTROSTATICALLY CHARGING SAID LATENT IMAGE AND DEVELOPING IT BY CONTACING THE SURFACE OF THE RECORDING MATERIAL WITH A COMPOSITION CONTAINING ELECTROSTATICALLY ATTRACTABLE TONER PARTICLES.

United States Patent Office 3,806,353 Patented Apr. 23, 1974 US. Cl.117-175 6 Claims ABSTRACT OF THE DISCLOSURE Copying process whichcomprises imagewise exposing to activating radiation a recordingmaterial comprising electrically conductive particles homogeneouslydispersed in a deformable insulating polymeric substance, said substancealso containing at least one substance capable of giving off a gas underirradiation, thermally expanding the gas thus released, to produce alatent image consisting of areas of different conductivity on saidrecording material, electrostatically charging said latent image anddeveloping it by contacting the surface of the recording material with acomposition containing electrostatically attractable toner particles.

The present invention provides a method of and material for recordingand reproducing information.

The method according to the invention comprises deforming,thicknesswise, a recording material of which at least part of thethickness, from its surface, is formed by a continuous phase of adeformable insulating matter which is laden, in direct contacttherewith, with electricity conductive particles, in homogeneousdispersion, so as produce, by varying the distance between theconductive particles, regions of different conductivity defining animage corresponding to the information to be recorded, and developingthe thus defined image into visible form.

By way of conductive particles, use can be made of both metallicparticles and non-metallic conductive particles, for example particlesof graphite and particles of conductive metallic oxides. By way ofmetallic particles, use can be made of particles of metals or of alloys,for instance highly conductive metals such as copper, iron, nickel,silver and aluminium. The shape of these conductive particles can beregular, e.g. spherical or oval, or be irregular (fragments produced bygrinding larger pieces). These particles may consist of a conductive ornon-conductive, porous or compact, core of which the surface is coatedwith conductive matter and of which the pores, if any, may containconductive matter. The grain size of these particles preferably liesbetween 0.1 and 100 microns. This grain size is preferably uniformwhereby the electric conductivity of the material in the initial state(before use) of the latter may be homogeneous. In some cases it mayhowever be of advantage, in order for the dispersion to be well filledwith conductive particles, to use particles of several well-definedgrain sizes so that the finest particles may come to be located in theinterstices between the largest particles. The concentration ofconductive particles in the dispersion preferably lies between 10 and80% by volume.

The concentration of the conductive particles in the deformableinsulating matter, the conductivity, the size, the shape of theseparticles and the resistivity of the insulating matter are preferably sochosen that there may be obtained a variation in the conductivity of thematerial in a ratio of at least 10 by varying the thickness of thematerial whereby an image having a good contrast and possibly agradation of the intensity of the various parts of the image may 'beobtained.

The absolute value of the initial resistivity and of the finalresistivity of the material is chosen in dependence on the way thelatter is to be used and on the method by which the resulting latentimage is developed. For example, material intended for electrostaticdevelopment preferably has an initial resistivity of the order of 10ohm.cm. and and a final resistivity, in its most resistive parts, of atleast 10 ohm.cm. Preferably, this latter resistivity is even of theorder of 10 ohm.cm. Material intended for electrolytic developmentpreferably has an initial resistivity of the order of for example 10ohm.cm. and a final maximum resistivity of the order of 10 to 10 ohm.cm.Of course, the greater the resistivity variation through deformation ofthe material, the better will be the contrast and the intensitygradation that can be obtained.

As regards the absolute value of the resistivity of the conductiveparticles as such, use is preferably made of particles of matters havingresistivities ranging for example from about 10- ohm.cm. to about 10"ohm.cm. As for the corresponding values for the deformable matter, theyrange for example from 10 to 10 ohm.cm.

The insulating matter may be deformed under the action of pressure or asa result of a change in temperature. This matter may for example havethe structure of a foam with open or closed cells, or a fibrousstructure, these two structures being deformable either by compressionor by heating. It may also contain small gas bubbles homogeouslydistributed in its mass or, in the case where it has a closed cell foamstructure, it may contain a gas inside the cells. The insulating mattermay also be in its initial state (before being subjected to the actionof mechanical stresses caused by a tension applied while being formed,e.g., while being put into sheet form). In this case, these stresses maybe interrupted by heating thereby causing a variation in the volume ofthe insulating matter. Material containing deformable insulating matterof this type is for example described in US. patent specification No.3,223,526.

The insulating matter may also contain, in homogeneous dispersion or insolution form, at least one swelling agent consisting of a substance ora mixture of substances capable of giving off at least one gas under theaction of heating above a certain temperature. The swelling agent ispreferably so chosen that this temperature will be higher than theambient temperature. By way of swelling agent, use can for example bemade of one of the swelling agents described in the followingpublications:

Chemistry and Industry, Mar. 31, 1962, pp. 572 to 576;

mula R-N in which the R group is an aryl or heterocyclic group, or agroup of formula R CO-- or R -SO R and R themselves being aryl orheterocyclic groups. Use can also be made by way of swelling agent of adiazonium salt, a diazo-oxide or a diazosulphonate. Another example ofthe swelling agent that can be used isN,N'-dimethyl-N,N-dinitroso-terephthalamide whose decompositiontemperature is '98 C.

In some cases it may be of particular advantage for the swelling agentto be so chosen that it only acquires its property of giving off gasafter having been sensitized or activated by irradiation with an actinicradiant action (electromagnetic waves capable of producing or ofinitiating chemical reactions including the most energetic part of thespectrum, i.e., radiations lying between the green part of the visiblespectrum and the gamma rays). For example, use can be made, by way ofphotoactivatable swelling agent, of ferriammonium oxalate and(N,N'-dimethylamino -p-diazobenzene fluoborate.

The deformation of the insulating matter can be either reversible orpermanent depending on the nature of the latter, in particular onwhether it is elastic or not. This deformation may mainly be due eitherto the deformation of the insulating matter as such or to the expansionof the gas that may be trapped within the substance.

The chemical composition of the deformable insulating matter may varywidely. This matter may consist of a thermoplastic polymer, e.g. apolyolefine, a polyvinyl resin, a polyacrylic or polymethacrylic resin,a polyamide, etc., of a thermosetting polymer, e.g. an epoxy resin, apolyester, etc., of an elastomer, e.g. a natural rubber, a syntheticrubber (polydiene), etc., of an elastic or rigid polyurethane foam withopen or closed cells. The deformable insulating matter may also consistof a mixture of different substances and it may have a homogeneous orheterogeneous structure. For example, it may simultaneously comprisefibres and a foam to form a heterogeneous deformable structure.

The deformable insulating matter may be transparent, translucid oropaque to visible light and/or other electromagnetic radiations. It maycontain in dispersion form, besides the conductive particles, opacifyingor coloring agents, or particles of substances having a large heatabsorbtion capacity and hence able to amplif the elfect of the heat.

Depending on the case, the entire thickness of the material or only partof this thickness may be formed by the deformable matter. In this latterevent, the remainder of the thickness of the material may be formed by asupport of which at least that part which is in contact with theconductive deformable matter is itself conductive. This support may, forexample, consist of a sheet of paper coated with a thin conductivelayer, e.g. aluminum foil, in contact with the conductive deformablematter. The conductive layer of the support may be used as an electrodeduring development of the image, since it forms an integral part of theactual recording material.

The layer of insulating matter may be applied to the support not only inthe form of a continuous layer but also in the form of a discontinuouslayer made up of strips, dots, smudges, etc., whether evenly distributedor not, the thickness of this discontinuous layer being however the samethroughout in the initial state of the material. The advantage of sodividing the layer is to avoid the phenomenon of tint weakening, at thecenter of layer regions having a large area, during electrostaticdevelopment, this well-known phenomenon being caused by a preferentialaccumulation of electric charges at the periphery of such regions.

The thickness of the deformable insulating part of the materialpreferably ranges from 5 to 500 microns. The thickness of the support ifany, also ranges from 5 to 500 microns and depends on the way thematerial is to be used and on the required mechanical strength.

As regards the general shape of the material, it can be very varied.Thus, the material can for example have a generally flat shape, forinstance in the form of flexible or rigid sheets, of strips, and ofsheets woundover the outer or inner surface of a cylindrical drum. Thematerial may also be in the form of a filament, of a flexible or rigidrod or bar of circular, oval or polygonal crosssection, etc.

The way in which the image is defined on the surface of the deformableinsulating matter depends on the nature of the latter.

When the deformable matter is one which is deformable under the actionof pressure, the image is defined by exerting on the support asuflicient pressure to cause a deformation which results in aconductivity variation enabling the subsequent development of the image.For this, a clich in relief of the desired image may be used.

When the insulating matter is deformable as a result of .4 a temperaturevariation, deformation may be brough about by the application of a hotplate carrying a clich in relief of the desired image. Preferably,however, use is made by way of heat source of an infra-red radiantsource, for instance an infra-red radiant source of a common type(called infra-red flash lamp) capable of emitting high-power radiationof for example 500 to 2000 watts in the form of an emission of shortduration, e.g. of 1000 microseconds with a maximum intensity peaklasting microseconds. The procedure may be similar to the so-calledflash thermography method, as described for example in British patentspecification No. 863,641, using for example, by way of image to berecorded, an image having more or less reflective and/or more or lessabsorbent parts and operating either by reflection or by transmission(through transparency), as described for example in the above Britishpatent specification or in US. patent specification No. 3,196,029.

For example, the heating operation may be performed by transferring,into the particle laden insulating matter, the heat accumulated inregions that absorb the infra-red radiations of an image formed on anoriginal document maintained in thermo-conductive contact with thematerial during irradiation of this document with radiations at leastmostly made up of infra-red rays. This can take place either bytransmission or by reflection. The latter method is of particularadvantage for making reproductions from thick documents, e.g. pages ofbooks.

The material can also be heated by the absorption of radiations, e.g.infra-red or visible radiations, in at least one substance contained inthe material and by the transformation into heat of at least part of theenergy from these radiations. For this purpose, a mask defining theimage on the surface of the material ma for example be placed betweenthe radiant source and the material.

In the case of the material containing a swelling agent capable ofgiving off a gas under the action of irradiation with activatingradiations, the action of this irradiation being possibly combined withthat of a heating operation, the image may for example be defined on thesurface of the material in the following way:

Between an activating radiations source, preferably a radiant sourceconsisting at least to a major extent of ultra-violet radiations, andthe material, there is placed a mask defining the image on the surfacethereof. The parts that are not covered by the mask are irradiated withactivating radiations so as to define the image in a latent form on thesurface of the insulating matter. This surface is then heated, eitherbefore or after removing the mask, so as to deform those parts that arenot or were not covered by the mask. The preferred form of heat sourcefor carrying out this latter operation is an infra-red flash lamp, e.g.a lamp having the above indicated characteristics.

The material used for carrying out the above described method may beemployed either as a definitive document or as an intermediate document,i.e. as a master. In this second case, the master may be used to produceseveral definitive documents (copies) or to produce one or more furthermasters. In this latter event, if the insulating mat ter is deformable,the material may resume its initial shape, once an image has beenrecorded in a visible (developed) form or in an invisible (latent image)form and this image has been transferred on to another master, thusenabling this same material to be re-used for recording new information.

In order to develop, i.e. to render visible, the latent image producedin the form of conductivity differences through deformation of thematerial, use is made of these conductivity differences. Depending onthe absolute value of the conductivity of the different regions of thematerial and on the relationship between the conductivity of one regionand that of another, different electrophotographic development processesmay be resorted to, these being known per se and forming no part of theinvention. Some of these processes are for example described in the onwhich the letters are to appear in recessed manner and the anode. After8 minutes of electrolysis at a temperature of 30 to 40 C. (v.=1 'v.;I=100 ma./dm. the letters appear in black on the copper coloredbackground of the recording material.

EXAMPLE 2 A recording material is prepared, similar to that of Example 1but comprising, in addition to the copolymer sheet laden with copperparticles, an aluminium sheet 15 microns thick with one side thereoflined with the copolymer sheet.

The procedure for preparing this material is the same as that forpreparing the material according to Example 1, the only difference beingthat the dispersion of copper in the copolymer is poured onto analuminium sheet 15 microns thick instead of being poured directly ontothe plate and that the sheet is left adhering to the aluminium sheetafter evaporation of the xylene.

The material according to this example is used in the same way as thataccording to Example 1, but with the aluminium sheet acting as theelectrode during electrolytic development of the signs recorded on thedeformable surface of the material.

EXAMPLE 3 Using the procedure of Example 1, a recording material isprepared consisting of a sheet having an initial thickness (before use)of 60 microns, laden with the same copper powder as that employed inExample 1, in the form of a suspension containing 10% by volume of copper, but using, by way of deformable insulating matter, a copolymer ofpolyvinyl-toluene and of polybutadiene having a resistivity of 3.3 10ohm.cm.

Letters are recorded on this material by striking characters with atypewriter, as indicated in Examples 1 and 2. At the bottom of the marksmade, the thickness of the material is 40 microns and the correspondingtransverse electric resistivity is 2x10 ohm.cm.

The image of the letters inscribed on the material are thenelectrostatically developed as follows:

The entiresurface of the material is subjected to a corona discharge, byscanning in a plane parallel to the surface of the material, with theaid of four tungsten wires 10 microns thick which lie parallel to eachother and which are also kept parallel to the material, at a distance of1 cm. from the surface of the latter, there being applied between thesewires and the material a potential difference of kv. There is thusformed on the surface that is exposed to the corona discharge a uniformsuperficial charge of electrons which lasts for some tens of seconds inthe most resistive parts of the material (those whose thicknesscorresponds to the initial thickness of the latter) but which dischargesin a few fractions of a second in the least resistive parts (those whichcorrespond to the bottoms of the recessed imprints of the letters).

The thus created electrostatic latent image is made visible by flowing amixture of toner powder (Rank-Xerox 04/E/007), having a grain size ofthe order of 5 microns, and of glass micropellets having a diameter ofthe order of 0.5 to 1 mm., over the surface of the material, when placedin an inclined position.

The toner powder remains fixed by electrostatic attraction to thecharged parts of the material and the letters thus become visible, byappearing with a copper coloring (the original colouring of thematerial) in a background having the coloring of the toner.

The image which has thus been made visible is fixed to the material assuch by uniformly heating, with the aid of an infra-red ray lamp, thesurface in such a way as to the melt on the surface the toner particles.

EXAMPLE 4 The procedure is as set forth in Example 3 but instead offixing the image on the actual material, the toner powder is transferredby adhesion on to a definitive document. After this transfer, powder isagain electrostatically applied on the material and the powder istransferred on to a definitive document. This cycle is repeated severaltimes so that a practically unlimited number of copies can be made of'the text that is recorded on the material.

EXAMPLE 5 The procedure is as set forth in Examples 3 and 4, using thematerial several times as a duplicating master, but the transfer of theimage from the initial material to the definitive documents is done byapplying an electric field between the material and the supports of thedefinitive documents.

EXAMPLE 6 The procedure is as set forth in Examples 3, 4 and 5 using forthe material a material comprising an aluminum sheet 15 microns thick onone side thereof, this aluminium sheet acting as an electrode during thecorona discharge and during the subsequent transfer of the image byelectrostatic attraction.

EXAMPLE 7 In a manner similar to that described in Example 2, arecording material is prepared consisting of an aluminium sheet 15microns thick which is coated on one of its sides, at a temperature of20 C., with a layer microns thick of a suspension containing 20% byvolume of tungsten powder (made up of spherical particles having ahomogeneous grain size very close to 2 microns) in a copolymer ofpolyacrylic resin and of polysteyrene known in the trade under the nameof Pliolite AC and made by Goodyear Tire and Rubber Company. For thepreparation of this suspension use is made of a 30% by weight solutionof Pliolite AC in xylene.

Pliolite AC has the following physical and electrical properties:

In this suspension, there is also incorporated 5% by weight ofN,N'dimethyl-N,N'dinitroso-terephthalimide which is a compound thatdecomposes when heated to a temperature of 98 C. by giving off nitrogenand which acts as a swelling agent for the dispersion layer.

An image is recorded on this material as follows:

Between the material and a 1000 w. infra-red lamp emitting 1000microsecond flashes with maximum intensity periods of 100 microseconds,is placed a mask formed by a stencil bearing a text made by perforatingwith a typewriter a suitable support that is highly resistant to heat.The material is irradiated for 30 seconds, with the infra-red lamp beingkept at a distance such from the material that the temperature of thatpart of its sruface which is exposed to the radiant action be raised toC., the remainder of this surface remaining at a temperature of lessthan 40 C.

The parts of the material that are exposed to the radiant action swellthicknesswise in an irreversible manner and come to have a thickness of250 microns. Their resistivity is then 10 ohm.cm. The unexposed parts ofthe material retain their original thickness and resistivity, i.e. 80microns and 2.5 X 10 ohm.cm.

Finally, the resulting latent image of the text is developed byelectrolysis, in the manner described in Example 1. There is thusobtained an image of the text having a metallic color, which stands outfrom the black background deposited by electrolysis on the unexposedparts of the surface of the material.

following work: Electrophotography, by R. M. Schafiert, The Focal PressLondon and New York (1965).

With some of these methods the image can be made to appear on thesurface of the actual material and with others the image can betransferred in visible or invisible (latent image) form from the surfaceof the material to that of another material whichmay be termed receivingmaterial or auxiliary support. This receiving material may -'be paper,either special or ordinary.

One method enabling the image to appear on the surface of the actualmaterial consists in charging the surface of the material, on theinsulating matter side, with positive or negative electrostatic charges,at a density which is an inverse function of the conductivity of thematerial. For this, any known means may be resorted to, e.g. a coronadischarge device. The latent'image that consists of regions of differentconductivity is thus transformed into a corresponding latent imageconsisting of regions that are electrostatically charged at the surface.The image can then be made visible by the so-called cascade method whichconsists in sprinkling the surface of the material with a powder whichhas been electrostatically charged by triboelectric friction and whichis made up of two kinds of particles, i.e. the toner, a black or coloredpowder whose tint or coloring contrasts with the initial tint orcoloring of the material, and the carrier, a coarser grained powderwhich serves to generate the electrostatic charges of the toner. Thetoner and the carrier are so chosen that the toner acquires a charge ofopposite sign to that of the charge of the material so that the tonerparticles are selectively attracted by the charged regions of the image,with the density of the particles corresponding to that of the charge ofthe various regions. With the surface of the material being placed in aninclined position, a large number of the toner particles areelectrostatically attracted by the charged regions of the image andbecome separated from the carrier particles to be deposited on thesurface of the material. All that remains to be done is to fix thetoner. particles on the surface of the material and this can be done bya slight heating action: when the binder is thermofusible at least in thstate in which itfinds itself in the image regions on which the tonerparticles become fixed, this heating action, if it is suitablyregulated, serves superficially to soften the material and to retain thetoner particles thereon. Once the binder has cooled and hardened, thetoner remains definitely fixed. By way of alternative, use can be madefor the toner of a substance which can be softened and/or become tackyupon being slightly heated and which remains definitely fixed aftercooling, e.g. a thermoplastic polymer. The toner can also be depositedon the charged regions of the material by other known methods, forinstance those which are also described in the above mentioned documente.g. the brushing method (fur brush or magnetic brush), the impressionmethod with a mohair roller, the method involving the production of acloud of powder, the method involving the production of an aerosol ofcharged liquid droplets, and the electrophoresis method.

It is also possible to deposit a powder having a coloring whichcontrasts with that of the dispersion without first charging the surfaceof the material, i.e. by directly using the latent image consisting ofregions of different conductivity. This may for instance be done byelectrolysis of a suitable substance, e.g. an aqueous solution of one ormore metal salts having colored ions having a suitable coloring, withthe cathode being formed by the material carrying the latent imageconsisting of regions of different conductivity. Another way is byelectrophoresis of a suspension of charged black or colored particleswith the material being used as the electrode of opposite sign to thatof the charge in the particles. In both cases, the ions and the chargedparticles are selectively attracted by the most conductive regions ofthe image and discharge themselves on these regions. It is also possibleto obtain a very progressive and extensive coloring intensity range byresorting to these latter two developing methods. The fixing of theimage, once developed, can be done in the above indicated manner. Onemethod for transferring the image from the surface of the material tothat of another material for example consists in first developing theimage on the material as such in the form of a deposit of black orcolored powder or particles, by one of the above described methods, butWithout fixing the powder, and in then transferring by contact, with theuse of an adhesive, and/or by electrostatic attraction, at least part ofthis powder in the form of an image on the receiving material. It isalso possible to transfer on to the receiving material the latent imageconsisting of electrostatic charges and produced as indicated earlierfrom the latent image that consists of regions of differentconductivity, and then make visible the image on this receiving materialby one of the above-described methods. It is also possible to form onthe receiving material the latent image that consists of electrostaticcharges by injecting such charges, directly using in so doing the latentimage that consists of regions of different conductivity of the originalimage.

EXAMPLE 1 A recording material, consisting of a sheet of copoly mer ofpolyvinyltoluene and of acrylic resin (resistivity of the copolymer: 6.3l0 0hm.cm) 45 microns thick and containing 50% by volume of copper inthe form of a homogeneous dispersion of copper particles, is prepared asfollows:

In 165 ml. of solution containing 30% by weight of copolymer in xylene,there is dispersed by vigorous agitation 445 g. of copper powder havinga grain size distribution as indicated in the table below:

Mean particle size (in microns) IQUIAUMUI The resulting dispersion isspread on a plate to form a film and the xylene is left to evaporate toproduce a flexible sheet having suflicient mechanical strength to enableit to be detached from the surface of the plate. The transverse electricresistivity of this sheet is 1.1)(10 ohm.cm.

Letters are then recorded on this material by striking thereoncharacters with an ordinary typewriter. With a normal striking force ofthe typewriter, the characters form recessed marks on the material whichretains a permanent deformation corresponding to a mean thickness of 20microns at the bottom of the marks. The corresponding transverseresistivity amounts to 25x10 ohm. cm. There is consequently obtained aresistivity variation having a factor of 10 between the deformed partsand the nondeformed parts of the material. The letters inscribed inrecessed form are then electrolytically developed as follows: the sheetof recording material bearing the impressed marks of the characters ispressed gently and uniformly between two flat nickel electrodes of anelectroplating apparatus after having applied a sheet of galvanoplasticpaper inbibed with an electroplating solution called black nickel havinga pH lying between 6.6 and 6.9 (composition of this solution, for 20litres of solution: ammoniacal nickel sulphate, 2 kg. dissolved in 7litres of distilled water; ammonium sulphate solution,

0.1 kg.+ammonium sulphocyanide, 0.6 g. in 2 litres of distilled water,zinc sulphate, 0.38 kg.+balance of distilled water for 20 litres)between the side of the material 9 EXAMPLE 8 In a way similar to thatdescribed in Example 7, a recording material is prepared, consisting ofa sheet of aluminium 15 microns thick which is coated on one sidethereof at a temperature of 20 C. with a layer 80 microns thick of asuspension containing 15% by volume of the same copper powder as thatemployed in Examples 1 and 3, in Pliolite AC which suspension alsocontains a 5% by weight dispersion of N,N-dimethyl-N,N'-dinitroso-terephthalamide.

The image of a text is recorded on this material in the same way as inExample 7 but so regulating the irradiating conditions that thetemperature of the exposed parts of the surface of the material may beraised to 140 C., and kept at that value for 30 seconds, the shieldedparts remaining at a temperature of less than 40 C. Between the exposedparts and the unexposed parts, there is thus obtained an electrostaticcontrast of 700 volts, with a residual potential of 200 volts for theunexposed parts, as a result of the swelling of the exposed parts whichcome to have a thickness of 280 microns whereas the unexposed partsretain their original thickness of 80 microns.

The image of a text typewritten with black ink'on ly from the thusobtained latent image and this developed image is fixed on the materialin the manner described in Example 3.

EXAMPLE 9 The procedure is as set forth in Example 8 but instead offixing the image of the text on the actual material, it is transferredby adhesion on to a definitive document as in Example 4 EXAMPLE 10 Theprocedure is as set forth in Example 8 but instead of fixing the imageof the text on the actual material, it is transferred electrostaticallyon to a definitive document as in Example 5.

EXAMPLE 11 In a manner similar to that described in Example 2, arecording material is prepared having the following characteristics:

conductive support: an aluminium sheet 15 microns thick deformablelayer, in the direction of its thickness (original thickness 80microns): a 15% by volume suspension of nickel powder (2-3 micron grainsize) in Pliolite AC swelling agent: (N,N'-dimethylamino)-p-diazobenzenefluoroborate (made by Gevaert and known in the trade under the name ofDiazo 69) (in a 10% by weight suspension in Pliolite AC) (decompositiontemperature of this swelling agent: 108 C.).

For the preparation of the deformable layer use is made of a 30% byweight solution of Pliolite AC in xylene, the solution also containingthe swelling agent. The nickel powder is mixed with this solution and isdispersed therein with an ultra-sonic agitator.

The image of a text typewritten with black ink on translucid paper isrecorded on this material by inserting this text between the materialand an ultra-violet ray emitting lamp (a 125 w. mercury vapour lampwhose emission spectrum has intensity peaks for the followingwavelengths: 2805, 2884, 2968, 3025, 3129, 3342, 3658, 4062, 4353, 5461,5780 and 6924 Angstrom). After exposure, the material is uniformlyheated by putting it in contact for 5 minutes with a hot metallic platehaving a temperature of 105 C.

With an irradiation period of 5 minutes there is obtained anelectrostatic contrast of 800 volts between the exposed parts of thesurface of the material and the unexposed parts thereof (these latterparts corresponding to the text), with a residual potential of 250 voltsfor the unexposed parts.

10 The image of the text is then electrostatically developed from theresulting latent image and the developed image is fixed on the materialin the manner described in Example 3.

EXAMPLE 12 A recording material is prepared in the same way as inExample 11, with the following characteristics:

conductive support: an aluminium sheet 15 microns thick deformable layer(original thickness of 60 microns): a 1.5% by volume suspension ofnickel powder (identical to that used in Example 11) in Pliolite ACswelling agent: N,N-dimethyl-N,N-dinitroso-terephthalamide, in 5% byweight dispersion in the acrylic resin polymer.

The image of a text printed in black on a white background is recordedon this material by placing the latter on the text and by irradiatingthe free surface of the material with infra-red rays emitted by the samelamp as in Example 7. The latent image of the text is formed byrefiection, the black parts of the document absorbing more radiantenergy and reaching a temperature greater than that of the white parts.After three seconds of irradiation, the thickness of the parts of thematerial overlying the black parts of the document reaches micronswhereas the parts of the material overlying the white parts retain theiroriginal thickness of 60 microns. The resulting electrostatic contrastis 300 volts with a residual potential of 100 volts for the parts of thematerial that have not swollen.

The image of the text is developed electrostatically and is fixed on thematerial in the manner described in Example 3.

EXAMPLE 13 The procedure is as set forth in Example 12 but instead offixing the image of the text on the actual material, it is transferredby adhesion onto a definitive document in a manner similar to thatdescribed in Example 4.

EXAMPLE 14 The procedure is as set forth in Example 12 but instead offixing the image of the text on the actual material, it is transferredelectrostatically onto a definitive document in a manner similar to thatdescribed in Example 5.

EXAMPLE 15 A recording material is prepared in a manner similar to thatdescribed in Example 2, with the following characteristics:

conductive support: an aluminium sheet 15 microns thick deformable layer(original thickness of microns): a suspension containing 5% by volume ofcopper powder identical to that described in Example 1 and 55% by volumeof talcum powder (1 micron grain size) in a copolymer of acrylic resinand of polystyrene, having a resistivity of 1.5 10 ohm.cm. and a viscoustransition temperature of 60 C. (a product known in the trade under thename of Pliolite AC and made by Goodyear Tire and Rubber Company).

A type written text is recorded on this material by a striking actionwith an instantaneous pressure of 2 kg./ mmfi. At the bottom of therecessed marks, the thickness of the material is 70 microns. There isthus obtained an electrostatic contrast of 450 volts with a residualpotential of 200 volts.

The image of the text then is developed electrostatically and is fixedon the actual material, in the manner described in Example 3.

I claim:

1. A method of recording and reproducing information, which comprises(a) imagewise exposing to activating radiation a recording material atleast part of the thickness of which,

from its surface, is formed by a continuous phase of a deformableinsulating organic polymeric material which is laden in direct contacttherewith, with electrically conductive particles, homogeneouslydispersed in said insulating organic polymeric material, said materialalso containing at least one substance capable of giving ofi at leastone gas under irradiation with activating radiation, to form a latentimage thereon,

(b) heating the surface of the recording material to expand the gasreleased by said substance in said material in the regions exposed toirradiation and to cause swelling of this material in said exposedareas, to produce a latent image consisting of regions of differentconductivity by varying the distance between the conductive particles,

(c) electrostatically charging said latent image, and

((1) developing said charged latent image on said recording material bycontacting the corresponding charged surface with a developercomposition containing electrostatically attractable toner particles toform a pattern on said toner particles thereon.

2. A method according to claim 1, in which said activating radiationconsists, at least in major part, of ultraviolet radiations.

3. A method according to claim 2, which comprises inserting a maskbetween a source of ultraviolet radiation and said recording material toimagewise expose said recording material to form a latent image thereon.

4. A method according to claim 1, which comprises charging said latentimage by a corona discharge.

5. A method according to claim 1, which comprises transferring theelectrostatic charge image onto a receiving material, and developing theelectrostatic charge image on said receiving material.

6. A method according to claim 1, which comprises directly transferringthe latent image onto a receiving material by injection of electrostaticcharges.

References Cited WILLIAM D. MARTIN, Primary Examiner M. SOFOCLEOUS,Assistant Examiner US. Cl. X.R.

96-1 R, 1.1; 1171.7, 8, 8.5, 9, 11, 93, 93.1 CD, 93.31, 227, 230; 2041,181; 34674 S, SB, SC

Dedication 3,806,353.Paul Heinzer, Geneva, Switzerland. COPYING PROCESSUTI- LIZING A RECORDING MATERIAL COMPRISING ELECTRI- CALLY CONDUCTIVEPARTICLES HOMOGENEOUSLY DIS- PERSED IN A DEFORMABLE INSULATING POLYMERICSUBSTANCE. Patent dated Apr. 23, 1974. Dedication filed Mar. 26,

1984, by the assignee, Battelle Memorial Institute.

Hereby dedicates to the People of the United States the entire remainingterm of said patent.

[Official Gazette May 29, 1984.]

Dedication 3,806,353.Paul Heinzer, Geneva, Switzerland. COPYING PROCESSUTI- LIZING A RECORDING MATERIAL COMPRISING ELECTRI- CALLY CONDUCTIVEPARTICLES HOMOGENEOUSLY DIS- PERSED IN A DEFORMABLE INSULATING POLYMERICSUBSTANCE. Patent dated Apr. 23, 1974. Dedication filed Mar. 26,

1984, by the assignee, Battelle Memorial Institute.

Hereby dedicates to the People of the United States the entire remainingterm of said patent.

[Oflicial Gazette May 29, 1984.]

